I have encountered several situations where I wanted to remove an attachment from a post but without a forced delete of the actual file.
For example both changing or removing a featured image and/or editing a gallery are fairly common edits.
When an image is shared among posts and it is removed from a single post it is deleted from the Media Library rather than just being removed as an attachment to a single post.
This would be a practical option as both immediate and bulk actions in the Media library.